Installation Manual

Prerequisites
98-152675-A Chapter 3: Installation 3-7
3333
Cobham Public
In particular, an Iridium system should not be used for safety services (e.g. ACARS, FANS)
while an Inmarsat transmitter is able to transmit. If a dual dissimilar SATCOM installation
(Inmarsat + Iridium) is required for redundancy of safety services, the two systems should
operate on a mutually exclusive basis. This may be achieved by a manual switch-over
arrangement between the systems, or by an automatic cooperative arrangement, such as
described in ARINC 781-7, Section 3.1.4.3.
If a GPS antenna is installed near the LGA-5005, it should preferably have an approval under
TSO-C190, as this implies better immunity to SATCOM transmissions than the older TSO-
C144. The separation distance between the antennas should be at least 1.8 m.
The isolation between the LGA-5005 and a GLONASS antenna should be at least 46 dB. This
typically corresponds to a a separation between the antennas of 10 m.
The separation distances above are guidelines only, as Cobham has no control over
properties of the antennas of other systems. As with all radio systems, ensuring non-
interference remains the responsibility of the installation designer.
Fuselage Structure
In addition to the 4 mounting holes, an RF connector hole must also be provided. The hole
dimensions should be diameter 30/28 max/min to ensure proper sealing by the antenna O-
ring. If a larger hole is required, the O-ring will not function and the installer should provide
an alternative pressurisation sealing arrangement.
Engines and APU inlets
The Installer must verify that the LGA-5005 is positioned out of the zone of influence of
the engines and APU inlets.